The present invention relates to a system for distributing and depositing fibrous material to form a web of fibers which is subsequently bonded together by any known expedient such as application of a bonding agent, mechanical force, heat, etc. to form an integral web.
The present invention is concerned with the dry formation of webs, such as webs of wood fibers, plastic fibers or the like, as opposed to conventional wet formation of webs. One of the problems encountered in dry formation of webs is uniform deposition of the fibers preparatory to bonding thereof wherein it is desired that the fibers be deposited in a uniform and continuous manner upon a suitable forming surface such as a moving foraminous wire or cylinder. It is conventional to use forming bells to distribute dry-formed fibers onto a web; however, prior bell former arrangements have not been totally satisfactory, especially in situations wherein the bell former is to perform a spreading function on the fibers passing therethrough; that is, those situations wherein fibers are delivered to the forming bell inlet from a relatively small source such as a small diameter conduit and are to be distributed by the forming bell to a forming surface having an operational width substantially exceeding that of the forming bell inlet. It is often desirable to utilize such a system since small fiber delivery conduits have many economic and operating advantages. For example, the conduits can deliver fibers from a relatively remote fiber supply system, multiple forming stations can be readily accommodated in a limited area, etc. Unfortunately, however, such prior art systems have the disadvantage of being unable to lay down a fiber web having a consistently uniform basic weight in the cross-machine direction.
It is therefore an object of the present invention to provide an improved fiber distribution and depositing apparatus including a forming bell of novel construction which is utilized to deposit a fibrous web having a uniform basis weight onto a forming surface, such as a wire, despite the fact that the inlet end of the forming bell is substantially smaller widthwise than the width of the forming surface and is thus able to receive and distribute fibers from a relatively small conduit. The present system provides for entrainment of ambient air into the bell former along with gaseously-entrained fibers entering same from the conduit to promote fiber separation and provide sufficient dilution so the fibers do not coalesce. In addition, the precise physical characteristics of the bell former, as will be hereinafter described in greater detail, promote a uniform spreading of the fibers across the forming surface width prior to deposition of the fibers thereon.